Method of minimal stress inducing ophthalmic lens blocking and associated system

Abstract

A method and associated implementing system eliminates much of the stress presently introduced by the bonding of ophthalmic lens blanks, or blanks to a holding device, namely a metal block. The method of attaching ophthalmic lens blanks to a blocking assembly comprises the steps of shaping a blocking assembly to take the shape of an ophthalmic lens blank surface of an ophthalmic lens, wherein the blocking assembly is not attached directly to the ophthalmic lens blank during shaping of the blocking assembly; and following the shaping of the blocking assembly, attaching the lens blank to the shaped blocking assembly.

Description

RELATED APPLICATIONS[0001]This application claims priority to U.S. patent application Ser. No. 62 / 821,537 filed Mar. 21, 2019 titled “Minimal Stress Inducing Lens Blocking System and Method.”BACKGROUND INFORMATION1. Field of the Invention[0002]The present invention relates to lens blocking, and more particular to a minimal stress inducing ophthalmic lens blocking method and system.2. Background Information[0003]In the manufacturing of ophthalmic lenses, a method for holding the front side of the lens blank in preparation for surfacing on the backside of the blank is required, which is commonly called blocking or lens blocking. At present, the most common lens blocking technique is to first have a metal piece, referred to as a block, placed a specific distance from the front surface of the lens blank, then after this is done, a bonding material is then injected between the lens blank and the block. While several materials have been used for this bonding, the most common are a low mel...

AI Technical Summary

Benefits of technology

The present invention provides a new way to block lenses that reduces stress compared to previous methods. It also includes a system to implement this method. This technique helps alleviate the issues associated with previous lens blocking techniques.

Problems solved by technology

The de-blocking process, namely the removal of the bonding or blocking material and the blocking material recycling process, is time-consuming and is prone to contaminating the laboratory with bits of the bonding material.

The wax is particularly troublesome since it is difficult to remove from the finished lens.

Many of the third parties applying antireflective coatings will not accept lenses made in a laboratory that uses wax due to contamination issues affecting the coating.

However, because of the types of metals used in this alloy, the metal blocking material is a hazardous substance and requires the use of personnel protective equipment and wastewater treatment to reduce employee exposure and reduce the release of the hazardous substances to the environment.

However, with plastic lenses almost completely replacing glass ophthalmic lenses, several issues have been introduced.

With conventional blocking techniques it is common practice to wait 40 minutes to 1 hour after blocking a lens before proceeding to the surfacing process to allow much of the stress in the blocked lens blank to be reduced, Unfortunately, as the lens blank is surfaced it becomes thinner and weaker and more likely to deflect in response to the stresses introduced during the blocking process even if the aforementioned “time after blocking” was allowed to elapse prior for the blank to stabilize prior to surfacing.

Depending upon the shape of the lens and the type of plastic lens blank, even small amounts of stress will result in lens distortions.

The resulting lack of support at the edge of a lens blank can cause issues when positive power lenses are manufactured.

With larger eyeglass frames the support problem for positive lenses worsens because with a larger frame comes a larger lens and the edge becomes thinner still.

Surfacing outside the supported area on a thin plastic lens presents significant challenges and typically is associated with the introduction of lens flaws or premature de-blocking of the lens.

Premature de-blocking can occur when the cutting tool pushes into the unsupported area of the lens, the lens deflects, and the tool suddenly takes an overly aggressive cut into the lens blank.

Such a cut in these conditions can produce forces beyond what the blocking material can withstand.

Unfortunately, this is a labor, and knowledge, intensive activity and too often occurs only after an unacceptable pair of lenses has had to be rejected or has prematurely de-blocked.

However, lens distortion can still be introduced in the unsupported area of the lens blank.

Without knowing this precisely the proper lens thickness cannot be achieved.

It is a common occurrence using the most prevalent blocking equipment that lenses are produced with the incorrect thickness, This occurs as a result of the surfacing equipment erroneously expecting the front surface to be at a specific location.

This occurs even when the blocking apparatus has been calibrated, Essentially anything that interferes with the spacing between the block and the blank in forming the blocking assembly, while the blocking material is solidifying, will cause a thickness problem in the finished lens.

If this motion is restricted uniformly the resulting finished lens will typically be too thin.

Further, if the restriction is uneven (i.e., not radially symmetrical in its effect), the block will tilt which will result in the introduction of prism as well as thickness problems in the finished lens.

Unfortunately, present typical LMS software is not aware of, and does not communicate to, the surfacing equipment regarding the true position of the front surface of the lens blank, The surfacing equipment along with the LMS simply assumes it was blocked correctly and if this is not the case a thickness error will likely ensue for the reasons described above.

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